45 Cambridge IGCSE Biology 0610. Syllabus for examination in 2016, 2017 and 2018.
18. Variation and selection
18.1 Variation Core
• Define variation as differences between
individuals of the same species • Distinguish between phenotypic variation and
genetic variation • State that continuous variation results in a
range of phenotypes between two extremes, e.g. height in humans
• State that discontinuous variation results in a limited number of phenotypes with no
intermediates, e.g. tongue rolling •
Record and present the results of investigations into continuous and discontinuous variation
• Define mutation as genetic change
• State that mutation is the way in which new alleles are formed
• State that ionising radiation and some chemicals increase the rate of mutation
Supplement
• State that phenotypic variation is caused by both genetic and environmental factors
• State that discontinuous variation is mostly caused by genes alone, e.g. A, B, AB and O
blood groups in humans
• Define gene mutation as a change in the base
sequence of DNA
• Describe the symptoms of sickle-cell anaemia • Explain how a change in the base sequence of
the gene for haemoglobin results in abnormal haemoglobin and sickle-shaped red blood cells
• Use genetic diagrams to show how sickle-cell anaemia is inherited
• State that people who are heterozygous Hb
S
Hb
A
for the sickle-cell allele have a resistance to malaria
• Explain the distribution of the sickle-cell allele in human populations with reference to the
distribution of malaria Teaching of human inherited conditions should be
done with sensitivity at all times.
46 Cambridge IGCSE Biology 0610. Syllabus for examination in 2016, 2017 and 2018.
18.2 Adaptive features Core
• Define adaptive feature as an inherited
feature that helps an organism to survive and reproduce in its environment
• Interpret images or other information about a species to describe its adaptive features
Supplement
• Define adaptive feature as the inherited
functional features of an organism that increase its fitness
• Define fitness as the probability of an organism
surviving and reproducing in the environment in which it is found
• Explain the adaptive features of hydrophytes and xerophytes to their environments
18.3 Selection Core
• Describe natural selection with reference to: – variation within populations
– production of many offspring – competition for resources
– struggle for survival – reproduction by individuals that are better
adapted to the environment than others – passing on of their alleles to the next
generation • Describe selective breeding with reference to:
– selection by humans of individuals with
desirable features –
crossing these individuals to produce the next generation
– selection of offspring showing the desirable
features
Supplement
• Describe evolution as the change in adaptive features of a population over time as the result
of natural selection • Define
the process of adaptation as the
process, resulting from natural selection, by which populations become more suited to their
environment over many generations
• Describe the development of strains of antibiotic resistant bacteria as an example of
evolution by natural selection • State the differences between natural and
artificial selection • Outline how selective breeding by artificial
selection is carried out over many generations to improve crop plants and domesticated
animals
47 Cambridge IGCSE Biology 0610. Syllabus for examination in 2016, 2017 and 2018.
19. Organisms and their environment
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